Preparation of polyolefin-based adhesives

Abstract

Disclosed is a polyolefin-based adhesive. The adhesive comprises a maleated polyolefin. The maleated polyolefin is let-down in a linear low density polyethylene (LLDPE). The let-down LLDPE is selected from those which have a melt index MI 2 within the range of 0.1 dg/min to 5 dg/min, preferably from 1 dg/min to 3 dg/min, and comprises a TREF soluble fraction having an intrinsic viscosity less than 0.9 dl/g. The adhesive composition can be used in multilayer polyolefin films and multilayer pipes.

We claim: 
     
       1. An adhesive composition comprising:
 (i) 2 to 30 wt. %, based upon the total weight of the adhesive composition, of a maleated polyolefin; and 
 (ii) a linear low density polyethylene (LLDPE), wherein the LLDPE comprises; 
 greater than 15 to less than 20 wt. %, based upon the total weight of the LLDPE, of a TREF soluble fraction in ortho-dichlorobenzene, wherein the TREF soluble fraction has an intrinsic viscosity of greater than 0.3 to less than 0.7 dl/g as measured in ortho-dichlorobenzene at 150° C., and wherein the LLDPE has a melt index MI 2  from 0.1 dg/in to 3 dg/min 
 
       wherein the TREF soluble fraction is measured from the peak area of the TREF curve below 45° C. 
     
     
       2. The composition of  claim 1 , wherein the maleated polyolefin is a maleated high density polyethylene (HDPE). 
     
     
       3. The composition of  claim 2 , the maleated HDPE has a grafted maleic anhydride content within the range of 0.5 wt % to 3.5 wt %. 
     
     
       4. The composition of  claim 1 , which further comprises a polyolefin elastomer. 
     
     
       5. The composition of  claim 4 , wherein the polyolefin elastomer is an ethylene-propylene rubber. 
     
     
       6. A multilayer film comprising a layer of the adhesive of  claim 1 . 
     
     
       7. A multilayer pipe comprising a layer of the adhesive of  claim 1 . 
     
     
       8. The composition of  claim 1 , wherein the TREF soluble fraction has an intrinsic viscosity of about 0.6 dl/g. 
     
     
       9. A process for producing a polyolefin-based adhesive, comprising:
 (i) blending 2 to 30 wt. %, based upon the total weight of the adhesive composition, of a maleated polyolefin; and 
 (ii) a linear low density polyethylene (LLDPE), wherein the LLDPE comprises: 
 greater than 15 to less than 20 wt.%, based upon the total weight of the LLDPE, of a TREF soluble fraction in ortho-dichlorobenzene, wherein the TREF soluble fraction has an intrinsic viscosity greater than 0.3 to less than 0.7 dl/g as measured in ortho-dichlorobenzene at 150° C., and wherein the LLDPE has a melt index MI 2  from 0.1 dg/min to 3 dg/min 
 
       wherein the TREF soluble fraction is measured from the peak area of the TREF curve below 45° C. 
     
     
       10. The process of  claim 9 , wherein the LLDPE is a reactor powder. 
     
     
       11. The process of  claim 9 , the maleated polyolefin has a maleic anhydride content within the range of 0.5 wt % to 3.5 wt %. 
     
     
       12. The process of  claim 9 , wherein the TREF soluble fraction has an intrinsic viscosity of about 0.6 dl/g. 
     
     
       13. The process of  claim 9 , wherein the maleated polyethylene is an maleated high density polyethylene (HDPE).